add snippet that shows how to decompose glyphs in a TTF

Snippets/decompose-ttf.py

@@ -0,0 +1,28 @@
+import sys
+from fontTools.ttLib import TTFont
+from fontTools.pens.recordingPen import DecomposingRecordingPen
+from fontTools.pens.ttGlyphPen import TTGlyphPen
+
+
+if len(sys.argv) != 3:
+	print("usage: decompose-ttf.py fontfile.ttf outfile.ttf")
+	sys.exit(1)
+
+
+src = sys.argv[1]
+dst = sys.argv[2]
+
+with TTFont(src) as f:
+    glyfTable = f["glyf"]
+    glyphSet = f.getGlyphSet()
+
+    for glyphName in glyphSet.keys():
+        if not glyfTable[glyphName].isComposite():
+            continue
+        dcPen = DecomposingRecordingPen(glyphSet)
+        glyphSet[glyphName].draw(dcPen)
+        ttPen = TTGlyphPen(None)
+        dcPen.replay(ttPen)
+        glyfTable[glyphName] = ttPen.glyph()
+
+    f.save(dst)